Shareholders' Equity And Earnings Per Share (Aggregate Fair Values Assigned To Each Component Of Tangible Equity Units Offering) (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2010	Dec. 07, 2010
DisclosureShareholdersEquityAndEarningsPerShareAggregateFairValuesAssignedToEachComponent [Line Items]
Units issued		4,600	[1]
Unit price		$ 50.00
Gross proceeds		$ 230,000
Issuance costs, including discount		7,353
Net proceeds	222,647
Equity Component
DisclosureShareholdersEquityAndEarningsPerShareAggregateFairValuesAssignedToEachComponent [Line Items]
Units issued		4,600	[1]
Unit price		$ 40.271818
Gross proceeds		185,250
Issuance costs, including discount		5,934
Net proceeds	179,316
Debt Component
DisclosureShareholdersEquityAndEarningsPerShareAggregateFairValuesAssignedToEachComponent [Line Items]
Units issued		4,600	[1]
Unit price		$ 9.728182
Gross proceeds		44,750
Issuance costs, including discount		1,419
Net proceeds	43,331
Other borrowings
DisclosureShareholdersEquityAndEarningsPerShareAggregateFairValuesAssignedToEachComponent [Line Items]
Net proceeds	43,331
Other borrowings | Equity Component
DisclosureShareholdersEquityAndEarningsPerShareAggregateFairValuesAssignedToEachComponent [Line Items]
Net proceeds	0
Other borrowings | Debt Component
DisclosureShareholdersEquityAndEarningsPerShareAggregateFairValuesAssignedToEachComponent [Line Items]
Net proceeds	43,331
Surplus
DisclosureShareholdersEquityAndEarningsPerShareAggregateFairValuesAssignedToEachComponent [Line Items]
Net proceeds	179,316
Surplus | Equity Component
DisclosureShareholdersEquityAndEarningsPerShareAggregateFairValuesAssignedToEachComponent [Line Items]
Net proceeds	179,316
Surplus | Debt Component
DisclosureShareholdersEquityAndEarningsPerShareAggregateFairValuesAssignedToEachComponent [Line Items]
Net proceeds	$ 0

[1] TEUs consist of two components: one unit of the equity component and one unit of the debt component.